Airborne Auxiliary Power Unit, abbreviated as APU, is a small turbine engine mounted on the tail of an aircraft. Its main function is to supply power and provide gas sources. Some APUs are capable of providing additive thrust to the aircraft. Specifically, before taking off from the ground, an aircraft may rely on a power and gas supply from the APU, rather than the ground power and gas source vehicles. While on the ground, the APU also supplies power and compressed air to ensure lighting and air-conditioning in the cabin and cockpit. During take-off of an aircraft, the APU can serve as a backup power source. After the aircraft is landed, lighting and air-conditioning of the aircraft are still maintained by power from the APU. The functions of APU influence the flight stability of the aircraft, which directly affects flight cost and quality of service of the aircraft.
The malfunction of APU turbine vane fracture and rotor shaft jam is a common malfunction of APU. When such malfunction occurs, the only solution is to replace the engine of APU, and therefore the maintenance cost is very expensive and usually twice with respect to the cost of normal repair. If the malfunction can be found in advance, the maintenance cost will be greatly reduced and the maintenance cycle will be shortened. The invention provides the monitoring method for the malfunction of turbine vane fracture and rotor shaft jam to meet the demands in the art.